


What Have I Done?

by holmesbrcthers



Category: Harry Potter - J. K. Rowling, Sherlock (TV)
Genre: AU: Sherlock and Lestrade are Death Eaters, AU: Sherlock-Harry Potter Crossover, Gen
Language: English
Status: In-Progress
Published: 2013-05-17
Updated: 2013-05-17
Packaged: 2017-12-12 03:50:17
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,566
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/806872
Author URL: https://archiveofourown.org/users/holmesbrcthers/pseuds/holmesbrcthers
Summary: <blockquote class="userstuff">
              <p>Greg Lestrade and Sherlock Holmes are summoned by the Dark Lord, and Sherlock doesn't want to go back, because he's learned to care for (some) muggles.</p>
            </blockquote>





	What Have I Done?

**Author's Note:**

> AU prompt provided by tumblr's pondering-the-doctor and ughbenedict. Based on a 'Sherlock' candid where Sherlock and Lestrade have their sleeves rolled up, exposing their forearms.
> 
> Thank you!
> 
> Disclaimer: I own nothing. Characters from 'Sherlock' belong to Sir Arthur Conan Doyle and to the BBC, and those from 'Harry Potter' belong to J.K. Rowling.

“The Dark Mark hasn’t been active in years, Sherlock,” Lestrade whispered to the tall man beside him. 

“Well it is now, can’t you feel it?” Sherlock answered sharply. Silence fell about the two men, but unsure what to say. It had been years since they had felt their marks burn and wriggle on their forearms, they’d almost forgotten what it felt like. But there it was, the unmistakable feeling etched into their skin, and Lestrade shuddered as he watched it move on his skin, slithering greedily all over his forearm. He closed his eyes tightly , and sighed deeply. He had thought this had all been behind them.

Apparently not.

“So what are we going to do now?” Lestrade asked quietly after a few moments of strained silence, opening his eyes and looking at his the man that stood by his side, the only man who knew all his secrets. Sherlock didn’t reply. His eyes moved slowly around the room, finally stopping as they found what they were looking for. He found John’s slight figure sitting at his favourite armchair, casually typing away at something on his laptop, a steaming mug of tea placed on the table next to him. Probably updating his blog, Sherlock thought absentmindedly. 

He let his eyes linger on his friend, taking him in. If it hadn’t been for John, he might’ve been excited to feel the Dark Mark awaken after so many years. He’d refused to believe that the Dark Lord had been defeated, and he had searched for months, but he had found no trace, and if the brilliant Sherlock Holmes couldn’t find the Dark Lord... Well. No one could.

Sherlock’s mind sent him reeling back to those dark times after his Lord’s downfall. He had integrated the muggle world, having to hide away from the persecutions and trials of the wizarding world. He might not care much for his life, but Sherlock had no intention of meeting the dementors and their infamous kiss, and so, reluctantly, he was forced to mingle with these lowly people. Sherlock had not minded hiding away his magic, his mind had always been his greatest asset, he was a Ravenclaw, after all, but these muggles... Idiots, they were. Some were even greater idiots than Crabbe and Goyle, and that, was saying something. Sherlock’s mind thought of Anderson, and he shook his head, disgusted. He let the thought slip away, letting his mind wander to a moment later in time.

One thing that he had learned to appreciate in this awful, disgusting world, were the cigarettes and the narcotics. It was something new, something he wasn’t even accustomed to hearing about during his time discussing with the workers in the Department of Misused Muggle Artifacts, but he quickly learned about them, where to procure them, and how to use them. It made his mind numb, and he relished in the feeling. It made his dealings with muggles so much easier.

But his mind had suffered from it, and he had had to kick his addiction. His brother, Mycroft, who had already infiltrated the muggle government to prepare the Dark Lord’s ascent, had helped him, although slightly disgusted that he had dabbled so far into the muggle ways. Sherlock had shrugged it off, his mind was clear, and that was all that mattered.

Lestrade, another Death Eater who had found his place in the muggle world, had found himself working for their police. It was an easy way to be on the lookout for others like them, but he had only found a few, and they wanted to stay hidden, so, he left them alone. But he still had to work cases, which were terribly difficult for the new detective to understand. If he had been back home, a few spells would’ve done the trick, and everyone would know what had happened in no time. But that wasn’t the case here. Lestrade, the Slytherin, had found himself having to use his mind for the first time in years.

That’s why he had asked for Holmes’ help. He knew the man had to use that big brain of his before the man went mad and took his own life. They helped each other, in that way. Sherlock used his mind, and Lestrade caught criminals, assuring his place of authority at Scotland Yard.

And then, one day, Sherlock, who was trying to act more muggle-like to keep his facade strong... One day, he’d met John.

Sherlock shook his head, pushing himself away from his reverie, and let his eyes travel along John’s form. His face wasn’t set in its usual stony expression, a smile was curling the ex-army doctor’s lips into a slight smile. Definitely not the blog then, Sherlock noted. Writing to Harry was much more probable.

The tall man let his mind wander off again, remembering the first time that he’d doubted everything he had taken for granted his whole life. John wasn’t like the others. He was brave, courageous, and loyal. More loyal than some of the Death Eaters, Sherlock had thought, thinking sourly of Malfoy. Sherlock had frozen in place as that thought had crossed his mind. Had he truly placed a muggle’s value of the one of a fellow pureblood? He remembered the moment clearly, his mouth gaping, and he had had to rest his weight on the wall of the flat that they shared together as the realization struck him. John, a muggle, had found a place in Sherlock’s cold heart.

And if John wasn’t so bad... Did that mean that the other’s weren’t so bad as well?

Mrs. Hudson. Molly. They weren’t so bad either.

Oh, Merlin, he’d thought to himself. What have I done?

Sherlock’s eyes softened the longer he looked at John, before the guilt lit his angular features. He had started hoping that the Dark Lord had truly been defeated: that way, he could spend the rest of his life alongside John, taking care of this man who had warmed his heart, and shown him the wrong-doings of his past. But here he was, sleeved rolled up, the Dark Mark burning on his forearm, and it tore at his soul. He didn’t want to drag John into all of this. He didn’t want his friend to be hurt.

Lestrade looked at Sherlock compassionately, understanding the man’s feelings, even though he didn’t voice any of them. The look on his face as he looked at John was enough for Lestrade. He himself had fallen for a muggle woman, and had married her. He didn’t want her to be hurt either. 

He rolled down his sleeve, silently, knowing far too well that Holmes would need time to process all of this, his mind racing through all the different possibilities. He sighed again.

“You know that you’re going to have to tell him, Sherlock,” Lestrade said quietly, “before it’s too late.” Sherlock tore his gaze away from his friend, only to drop it to the detective’s face, a pained expression marking his features.

“I know, Greg,” he said, using the man’s first name for the first time. It felt like a farewell to their new lives, an acknowledgement that soon enough, everything that they’d grown to understand and appreciate, love, even, would disappear.

Lestrade opened his mouth to say something, but before even a breath had come out, both men were startled out of their dark thoughts by John’s voice. Sweet, innocent and naïve John. “Sherlock...? I think I’ve found something,” he called out. Both men exchanged quick glances and the detective saw Sherlock’s lips move quickly and quietly, mouthing ‘I’ll call you,’ and he nodded, leaving the two men alone in the flat. Sherlock sighed, and pulled at his sleeve as he walked over to where John was sitting, staring at his laptop.

“What is it, John?”

John looked up at Sherlock and pointed at his screen as he started speaking. “Well, I don’t know if it’s much, really, but there’s this rumour spreading over London that there are these... I don’t know really, I guess they’re this supremacist group... Anyways. There’s this rumour saying that they’re tracking down lost soldiers, people who’d left because the leader fell, it’s a long story really.”

Sherlock’s face paled as he listened to John ramble on, and he moved slowly to place himself behind John so he could see what he was pointing at.

“But the interesting part, is that there’s this old abandoned church ruin or something where they meet up, and it seems to be their headquarters, even if the satellite shows empty lands stretching out. So, naturally, I thought of tunnels, but hey, I’m just guessing here. What they do tell us, though, is that these soldiers, or whatever you want to call them, have these tattoos on their forearms...”

Sherlock’s steps faltered as he kept walking, and he closed his eyes as he got behind John, already knowing what he would see when he opened them.

“They’re these big snakes coming out of a skull’s mouth.”

Sherlock opened his eyes, the Dark Mark staring back at him from John’s laptop. He almost thought that he heard the Dark Lord’s maniacal laughter resonating behind his ears as the picture looked back at him, those empty eye sockets looking right into his soul, and he felt the mark on his arm crawl greedily.

Oh, John, he thought. I am so, _so_ sorry.

**Author's Note:**

> Hi everyone!
> 
> I hope you all enjoyed this little crossover, I was very much inspired, and I thoroughly enjoyed writing it. I hope that it is as enjoyable to read. Please, do not hesitate to leave constructive criticism, it is always appreciated. Let me know what you think. I'd also like to know if anyone would want me to continue this story...
> 
> Thank you so very much.
> 
> (Thanks again to tumblr's pondering-the-doctor and ughbenedict for this incredible AU prompt.)


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